Percutaneous transluminal coronary angioplasty (PTCA) is used to increase the lumen diameter of a coronary artery partially or totally obstructed by a build-up of cholesterol fats or atherosclerotic plaque. Typically a first guidewire of about 0.038 inches in diameter is steered through the vascular system to the site of therapy. A guiding catheter, for example, can then be advanced over the first guidewire to a point just proximal of the stenosis. The first guidewire is then removed. A balloon catheter on a smaller 0.014 inch diameter second guidewire is advanced within the guiding catheter to a point just proximal of the stenosis. The second guidewire is advanced into the stenosis, followed by the balloon on the distal end of the catheter. The balloon is inflated causing the site of the stenosis to widen. The dilatation of the occlusion, however, can form flaps, fissures and dissections which threaten reclosure of the dilated vessel or even perforations in the vessel wall.
Although the dimensions in the above example are suited to the coronary arteries, any body lumen can be treated by percutaneous transluminal angioplasty (PTA), including the vas deferens, ducts of the gallbladder, prostate gland, trachea, bronchus and liver or larger arteries such as the renal and carotid. The body lumens range in diameter from small coronary vessels of 3 mm or less to 28 mm in the aortic vessel. The invention applies to acute and chronic closure or reclosure of body lumens.
Guiding catheters are used to pass larger interventional devices which are passed through guiding catheters such as balloon catheters, balloon catheters with a stent crimped thereon, laser devices or atherectomy devices. The distal end of a guiding catheter is typically preformed into a curve specifically designed to conform to the vasculature of the target site as for example, the Amplatz or Judkins curves. Larger interventional devices typically have an enlarged distal working end. Friction builds up in the curve of a guiding catheter when large interventional devices are passed through the guiding catheter curve.
After deployment, the interventional device is withdrawn into the guiding catheter for removal. Die injection flow through the guiding catheter is restricted when such large interventional devices are retracted into the guiding catheter. The interventional device can also snag on the distal end of the guiding catheter when withdrawn into the guiding catheter.
Prior art catheters typically have a shaft with an inner diameter and outer diameter which remain constant along the length of the shaft as seen in commonly owned, copending U.S. Ser. No. 08/543,992 (WO 97/14466) to Brin et al. for a "Guide Catheter with Soft Distal Segment" which discloses a guiding catheter with a flexural stiffness gradation along the length of the catheter.
Commonly owned U. S. Pat. No. 4,563,180 to Jervis et al. for "High Flow Catheter for Injecting Fluids" discloses a catheter with an inside diameter which varies over its length from a minimum at the proximal end to a maximum at the distal end. It is not necessary that the transition from the minimum inside diameter to the maximum inside diameter occur gradually and uniformly. However, it is particularly preferred that the inside diameter tapers toward the proximal end of the catheter.
It is an object of the invention to optimize the design of a catheter for delivering large interventional devices through guiding catheters which minimizes friction build-up in the curved area of the guiding catheter while maximizing fluid flow. It is a further object of the invention to reduce the possibility of interventional devices snagging on the distal end of the guiding catheter when the interventional device is withdrawn into the guiding catheter.